Evaluation of a Pseudotyped Virus Neutralisation Test for the Measurement of Equine Influenza Virus-Neutralising Antibody Responses Induced by Vaccination and Infection

Abstract

Equine influenza is a major respiratory disease of horses that is largely controlled by vaccination in some equine populations. Virus-neutralising antibodies, the mainstay of the protective immune response, are problematic in assaying for equine influenza virus, as most strains do not replicate efficiently in cell culture. Surrogate measures of protective antibody responses include the haemagglutination inhibition (HI) test and single radial haemolysis (SRH) assay. For this study, a pseudotyped virus, bearing an envelope containing the haemagglutinin (HA) from the Florida clade 2 equine influenza virus strain A/equine/Richmond/1/07 (H3N8), was generated to measure HA-specific neutralising antibodies in serum samples (n = 134) from vaccinated or experimentally-infected ponies using a pseudotyped virus neutralization test (PVNT). Overall, the results of PVNT were in good agreement with results from the SRH assay (100% sensitivity, 68.53% specificity) and HI test (99.2% sensitivity, 49.03% specificity). The PVNT was apparently more sensitive than either the SRH assay or the HI test, which could be advantageous for studying the antibody kinetics, particularly when antibody levels are low. Nevertheless, further studies are required to determine whether a protective antibody level can be defined for the SRH assay and to ascertain the inter-laboratory reproducibility. In conclusion, the PVNT efficiently measures neutralising antibodies after immunization and/or experimental infection in the natural host, and may complement existing antibody assays.

Exploring Rapid and Effective Screening Methods for Anti-SARS-CoV-2 Neutralizing Antibodies in COVID-19 Convalescent Patients and Longitudinal Vaccinated Populations

“…Many methods for the detection of SARS-CoV-2 nAb have been described previously [17,[22][23][24][25], e.g., plaque reduction neutralization test (PRNT), cytopathic effect (CPE) of live SARS-CoV-2 and pseudovirus neutralization tests (PVNT), which are cost-and time-consuming, and cannot be widely implemented [26][27][28][29]. To date, most serology tests mainly detect IgM or IgG antibodies against SARS-CoV-2.…”

Systematic Review of Equine Influenza A Virus Vaccine Studies and Meta-Analysis of Vaccine Efficacy

“…More recently, the use of pseudotyped viruses, which package a reporter gene that provides a convenient read-out, have been developed for a wide range of viruses, and their use to measure neutralising antibody responses has gained wider acceptance during the COVID-19 pandemic [61]. The potential application of a pseudotyped virus neutralisation test to measure antibody responses in equine influenza vaccine efficacy studies has been described [62]. This has yet to be fully characterised to determine whether it can provide a correlate of protection or to define seroconversion.…”

Studying longitudinal neutralising antibody levels against Equid herpesvirus 1 in experimentally infected horses using a novel pseudotype based assay

“…A delta envelope (∆env) PV bearing no envelope GPs, plus a cell only control were included to define a threshold for successful PV production, and for cellular auto-fluorescence/luminescence background. An equine influenza (EIV) PV bearing both the haemagglutinin (HA) and neuraminidase (NA) surface GPs from the Florida clade 2 EIV strain A/equine/Richmond/1/07 (H3N8) (GenBank accession number: KF559336.1) was produced as previously reported and utilised as a positive control for the titration procedure ( Kinsley et al., 2020 ; Scott et al., 2016 ). Plates were incubated for 48 h at 37℃ at 5 % CO 2 before reading.…”